August 06, 2020 5 min read
By: Fiona Smeaton
In my last post, we discussed the amazing diversity of bees in Oregon. We also covered what is threatening these essential creatures. It is important for us as critical gardeners to support these pollinators in the city as they provide such essential ecosystem services. This week we are going to explore how we can start to identify these pollinators and monitor them so as to better support them in our own gardens.
First, I want to mention the amazing organization that created the protocol I will be referring to in this blog series. The Xerces Society for Invertebrate Conservation is a nonprofit organization headquartered here in Portland. They specialize in protecting invertebrates from extinction and educating the public about all the incredible services they provide. The main identification guide that I used for my master’s project was The Maritime Northwest Citizen Science Monitoring Guide by the Xerces Society. (https://xerces.org/publications/id-monitoring/maritime-northwest-citizen-science-monitoring)
This guide is focused on native bee identification and so the first step is to distinguish bees from wasps and flies, which can be difficult, especially with mimic species. There are certain characteristics that can help to distinguish these insect groups without having to collect or pin them. Bees have two pairs of wings, large eyes located on either side of their head, and long and bent antennae. Their bodies tend to be rounder, fuller and hairier than flies and wasps. Many female bees have scopa or corbicula, which are specialized clumps of hair, that hold large amounts of pollen on their legs or abdomen.
Flies tend to have very short antennae and they have large eyes that tend to meet at the top of the head. They only have one set of wings and they tend to be less hairy as well as lack pollen carrying structures, though they do transport grains of pollen that stick to their body. The flight behavior between bees and flies can also reveal their identity. Many flies will hover above or around flowers while bees will not, with the exception of carder bees.
Wasps do have two sets of wings, but their bodies are narrower than bees and pinched where the abdomen and thorax meet. They have less hair than bees and have coloration directly on their exoskeleton instead of on hairs, they also lack pollen carrying structures and only pollinate through the few pollen grains that might stick to them after visiting flowers.
Since bees are the most effective pollinators, of the majority of Portland flowers, we will spend the most time evaluating them. It is important to think about how a bee might interact with its environment in order to best support it. The bee lifecycle is made up of four stages: egg, larva, pupa and adult. The time that bees are observed visiting flowers and transporting pollen is a relatively small window of their overall life span. This time frame can range from a few days to weeks and may occur at different times throughout the blooming season. When female adult bees first emerge from their nests they mate and then spend the rest of their life foraging and provisioning for a nest of their own brood. The timing of their emergence varies greatly across genera and some species will have multiple generations emerge within a single year.
Bee nest placement and nest architecture define vital preferences in terms of habitat. Bees spend the majority of their life inside a nest and the rest of their time foraging and preparing a nest for their own brood. This means that availability of nesting materials is incredibly important in determining where native bees will inhabit and therefore pollinate. The majority of native bees, both solitary and social, nest underground, while others nest in hollow stems of plants or other available cavities. Social bumble bees commonly nest under woody plants or tall grasses. Queen bumble bees will often overwinter beneath leaf litter, even in areas where there are no floral resources, before they emerge in spring to start a new colony.
Note on Non-Native Honeybees:
The European honeybee is not a native to North America unlike the other wild bees mentioned here. They were brought to North America in the early 1600’s by European colonizers in order to expand honey production and they quickly spread throughout the United States. They have not evolved alongside the native flora of the Pacific Northwest or the native insects in the area. Honeybees are highly attuned to human activity and are easily managed and transported to fit anthropogenic needs. This means that they can have potential negative impacts on native wild bees in the area. There have been studies that show that honeybees can deter native bees from a foraging area, especially certain solitary bees that would avoid such direct competition. Additionally, the fact that honeybees are non-native to North America provides them with an advantage in the arms race against predators. It is still important to support honeybees as they are such great pollinators of many of the food crops we enjoy, but it is also essential to be mindful of native bees needs and how they might vary compared to honeybees.
Check out these other helpful identification guides:
Jackson, A. (2019). The Bees of the Willamette Valley: A Comprehensive Guide to Genera.
Jordan, S., Hopwood, J., Evans, E., Gill, K., Code, A., Frischie, S., Stiles, P. (2019). Habitat Assessment Guide for Pollinators in Yards, Gardens, and Parks. The Xerces Society for Invertebrate Conservation.
Mader, E., Shepherd, M., Vaughan, M., Hoffman Black, S., LeBuhn, G. (2011).The Xerces Society Guide: Attracting Native Pollinators: Protecting North America’s Bees and Butterflies. Storey Publishing.
I have always been passionate about connections between species in the natural world, I love to learn about organisms that have coevolved and formed mutually beneficial relationships. That is what first drew my attention to insect pollinators. I think that it is fascinating that these tiny creatures can play such a keystone role in an ecosystem. There would not be the incredible diversity of plants we know today without these insects. However, pollinators are currently facing a multitude of threats caused by humans' destructive practices on the modern landscape. Urban environments, while very disturbed and fragmented can provide valuable habitat for native pollinators. My Master’s program allowed me to investigate eight urban sites across Portland OR to find out which insect pollinators were observed in the summer of 2019 and which flowers they were visiting. My work was directed at urban land managers in Portland in order to help them strategize ways to create pollinator habitat around us. Now I want to share this information with the Cornell Farm community! This blog mini-series is meant to share my experiences monitoring insect pollinators and strategies I have learned in order to better understand how we can support these incredible species within our city.
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